12,297 research outputs found
Investigation of long-lived eddies on Jupiter
Quasi-geostrophic, two layer models of the Jovian atmosphere are under development; these may be used to simulate eddy phemonena in the atmosphere and include tracer dynamics explicitly. The models permit the investigation of the dynamics of quasi-geostrophic eddies under more controlled conditions than are possible in the laboratory. They can also be used to predict the distribution and behavior of tracer species, and hence to discriminate between different models of the mechanisms forcing the eddies, provided suitable observations can be obtained. At the same time, observational strategies are being developed for the Near Infrared Mapping Spectrometer on the Galileo Orbiter, with the objective of obtaining composition measurements for comparison with the models. Maps of features at thermal infrared wavelengths near 5 micron and reflected sunlight maps as a function of wavelength and phase angle will be obtained. These should provide further useful information on the morphology, composition and microstructure of clouds within eddy features. Equilibrium chemistry models which incorporate advection may then be used to relate these results of the dynamical models and provide addtional means of classifying different types of eddies
Stability of Chiral Luttinger Liquids and Abelian Quantum Hall States.
A criterion is given for topological stability of Abelian quantum Hall
states, and of Luttinger liquids at the boundaries between such states; this
suggests a selection rule on states in the quantum Hall hierarchy theory. The
linear response of Luttinger liquids to electromagnetic fields is described:
the Hall conductance is quantized, irrespective of whether edge modes propagate
in different directions.Comment: 12 pages, LaTeX (RevTeX 3.0
Density of quasiparticle states for a two-dimensional disordered system: Metallic, insulating, and critical behavior in the class D thermal quantum Hall effect
We investigate numerically the quasiparticle density of states
for a two-dimensional, disordered superconductor in which both time-reversal
and spin-rotation symmetry are broken. As a generic single-particle description
of this class of systems (symmetry class D), we use the Cho-Fisher version of
the network model. This has three phases: a thermal insulator, a thermal metal,
and a quantized thermal Hall conductor. In the thermal metal we find a
logarithmic divergence in as , as predicted from sigma
model calculations. Finite size effects lead to superimposed oscillations, as
expected from random matrix theory. In the thermal insulator and quantized
thermal Hall conductor, we find that is finite at E=0. At the
plateau transition between these phases, decreases towards zero as
is reduced, in line with the result
derived from calculations for Dirac fermions with random mass.Comment: 8 pages, 8 figures, published versio
Quasiholes and fermionic zero modes of paired fractional quantum Hall states: the mechanism for nonabelian statistics
The quasihole states of several paired states, the Pfaffian, Haldane-Rezayi,
and 331 states, which under certain conditions may describe electrons at
filling factor or 5/2, are studied, analytically and numerically, in
the spherical geometry, for the Hamiltonians for which the ground states are
known exactly. We also find all the ground states (without quasiparticles) of
these systems in the toroidal geometry. In each case, a complete set of
linearly-independent functions that are energy eigenstates of zero energy is
found explicitly. For fixed positions of the quasiholes, the number of
linearly-independent states is for the Pfaffian, for the
Haldane-Rezayi state; these degeneracies are needed if these systems are to
possess nonabelian statistics, and they agree with predictions based on
conformal field theory. The dimensions of the spaces of states for each number
of quasiholes agree with numerical results for moderate system sizes. The
effects of tunneling and of the Zeeman term are discussed for the 331 and
Haldane-Rezayi states, as well as the relation to Laughlin states of electron
pairs. A model introduced by Ho, which was supposed to connect the 331 and
Pfaffian states, is found to have the same degeneracies of zero-energy states
as the 331 state, except at its Pfaffian point where it is much more highly
degenerate than either the 331 or the Pfaffian. We introduce a modification of
the model which has the degeneracies of the 331 state everywhere including the
Pfaffian point; at the latter point, tunneling reduces the degeneracies to
those of the Pfaffian state. An experimental difference is pointed out between
the Laughlin states of electron pairs and the other paired states, in the
current-voltage response when electrons tunnel into the edge. And there's more.Comment: 43 pages, requires RevTeX. The 14 figures and 2 tables are available
on request at [email protected] (include mailing address
Hierarchical wave function, Fock cyclic condition and spin-statistics relation in the spin-singlet fractional quantum Hall effect
We construct the hierarchical wave function of the spin-singlet fractional
quantum Hall effect, which turns out to satisfy Fock cyclic condition. The
spin-statistics relation of the quasi-particles in the spin-singlet fractional
quantum Hall effect is also discussed. Then we use particle-hole conjugation to
check the wave function.Comment: 23 pages, PHYZZ
Would you give art to a drowning man?
A symposium to launch the research publication, "PLOT" Organised by Simon Read and Nicky Coutts introduced by Simon Read, artist, senior lecturer in Fine Art with presentations by Maria Thereza Alves, artist,Bergit Arends, curator, Natural History Museum, Dr Jean Fisher, Middlesex University, Fernando Rodriguez Palma, artist, summing up by Dr Martha Fleming.
Held at MODA (Museum of Domestic Arhitecture), Middlesex Universit
The X-ray Properties of the Nearby Star-Forming Galaxy IC 342: The XMM-Newton View
We present the X-ray properties of IC342 using XMM-Newton. Thirty-five
sources are detected coincident with the disk of IC342 (more than tripling the
number known), of which ~31 are likely to be intrinsic to IC342. This
population shows a range of spectral properties and has an X-ray luminosity
function slope and infrared luminosity comparable to that of starburst galaxies
such as M82 and the Antennae, while its relative lack of extended X-ray
emission is similar to the properties of quiescent spirals. We do detect
long-term variability between this observation and the 1991 ROSAT and 1993/2000
ASCA observations for five sources. Notably, the second most luminous source
IC342 X-2 is is found to be in its the lowest luminosity state observed for X-2
to date, although the slope of the spectrum is intermediate between the
previously observed low/hard and high/soft states. IC342 X-1, on the other
hand, is found to be in an identical state to that observed in 2000 with ASCA.
Assuming X-1 is in an anomalous very high (VH) state, then either (1) X-1 has
remained in this state between 2000 and 2002, and is therefore the longest
duration VH-state binary ever observed, or (2) it was simply caught in a VH
state by chance in both the 2000 ASCA and 2002 XMM-Newton observations. We have
also confirmed the ROSAT HRI result that the nucleus of IC342 is made up of
both point-like and extended emission. The relative fluxes of the two spectral
components suggest that the nucleus is complex, with a soft extended component
contributing approximately half of the total luminosity. (Abridged)Comment: AJ in press (December 2003), 9 pages, 7 figures, 2 tables,
emulateapj.cls use
Condensation of `composite bosons' in a rotating BEC
We provide evidence for several novel phases in the dilute limit of rotating
BECs. By exact calculation of wavefunctions and energies for small numbers of
particles, we show that the states near integer angular momentum per particle
are best considered condensates of composite entities, involving vortices and
atoms. We are led to this result by explicit comparison with a description
purely in terms of vortices. Several parallels with the fractional quantum Hall
effect emerge, including the presence of the Pfaffian state.Comment: 4 pages, Latex, 3 figure
Interaction between static holes in a quantum dimer model on the kagome lattice
A quantum dimer model (QDM) on the kagome lattice with an extensive
ground-state entropy was recently introduced [Phys. Rev. B 67, 214413 (2003)].
The ground-state energy of this QDM in presence of one and two static holes is
investigated by means of exact diagonalizations on lattices containing up to
144 kagome sites. The interaction energy between the holes (at distances up to
7 lattice spacings) is evaluated and the results show no indication of
confinement at large hole separations.Comment: 6 pages, 3 figures. IOP style files included. To appear in J. Phys.:
Condens. Matter, Proceedings of the HFM2003 conference, Grenobl
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Modeling the martian atmosphere with the LMD global climate model
Introduction: For several years we have been developing a 3D Global Climate Model (GCM) for Mars derived from the models used on Earth for weather forecasting or climate changes studies [1]. The purpose of such a project is ambitious: we wish to build a 'Mars simulator' based only on physical equations, with no tailor-made forcing, but able to reproduce all the available observations of the Martian climate (temperatures, winds, but also clouds, dust, ices, chemical species, etc...).
The GCM is constantly evolving, thanks to a contnuous collaboration between several teams based in France (LMD, SA), the UK (The Open University, University of Oxford) and Spain (Instituto de Astrofisica de Andalucia), and with the support of ESA and CNES.
We are currently working on an improved version of the model. Several new parametrisation are included in the heart of the model (radiative transfer, surface and subsurface processes, dynamics) and the applications of the GCM are in contnuous development (Water, dust, CO2, radon cycles, photochemistry, thermosphere, ionosphere, etc...
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